Guide vane for axial flow screw fans, propellers, pumps, and the like



oct- 10, 1950 1', ADAMTcHlK 2,524,869

GUIDE VANE FUR AXIAL FLOW SCREW FANS,

PROPELLERS, PUMPS, AND THE LIKE Filed Sept. 15, 1945 w if -s 1 9 loPatented Oct. 10, 1950 GUIDE VANE FOR AXIAL FLOW SCREW FAN S; PROPELLEPUMPS, AND Tr p Michael Thaddius Adamtchik, Brighton, England, assignorof one-half to James Russell Kennedy, London, England.

Application September 15, 1945, Serial No. 616,562 In Great BritainJanuary 19, 1945 3 Claims.

This invention relates to guide vanes, which operate in conjunction withacting propellers, such as rotors of axial flow fans, pumps, turbinesand the like.

According to the vortex theory of the screw propeller, there is nofundamental diiference between acting propellers and guide vanes. Thistheory can thus be applied equally to both types of propeller becausethe circulation which is produced by the acting propeller is transmittedfully to the re-acting propeller, the axial velocity of the flow beingthe same in both cases. whilst the relative peripheral velocity of flowmay vary considerably. This is due to the fact that the relativeperipheral velocity of the guide vane is equal to the rotationalinterference, which (as explained in my co-pending specification No.616,563) varied from the tip to the root.

The term circulation in aerodynamics and hydrodynamics is defined as theintegral of the tangential velocity component taken round the curve andthe value is represented by the expression:

K=I V cos ads where The rotational interference is the rotation of theslipstream produced by the circulation. The aim of the present inventionis to find the most efficient guide vane for any acting propeller whichproduces either constant or varying circulation along the blade, forexample such as described in my patent specification No. 616,563.

This specification describes a blade in which the circulation increasescontinuously from the hub to the tips of the blade.

As the rotational interference, as explained in the above mentionedco-pending specification, is proportional to the "circulation" andinversely proportional to the distance of the section from the centre,it follows that for a constant circulation the rotation interferencedecreases rapidly towards the tip.

With increasing the circulation" towards the tip, the decrease ofrotational interference is compensated, the limit to which thecirculation" can be increased being such as to produce constantrotational interference along the length of the blade.

The object of the present invention is to provide themost effectiveguide vane for operation in conjunction with the acting propellerhereinbefore mentioned.

Thus, considering the blades of the above acting propeller we have (1)increasing circulation towards the tip, (2) the axial velocity of flowincreasing slightly towards the tip, (3) constant rotationalinterference along the blade.

It is therefore evident that the resultant relative velocity of flowtowards the vanes of the guide vane, which is resultant of therotational interference and axial velocity of flow, increases onlyslightly towards the tip.

The increased circulation towards the tips of the vanes can be achievedby increasing the lifting force of the vanes towards the tips. Thisisefiected by the increase of the following parameters:

(1) The relative curvature of the section (2) The width of the section(3) The geometrical pitch of the section.

The relative curvature of a section is the ratio of the maximum ordinatetaken from the tangent chord to the centreline of the section to thewidth of the chord.

The geometrical pitch is given by the formula:

21rR Tan (1) Where R is the distance of the section from the centre. (pis the angle between the tangent chord and the axis.

The geometrical pitch of the guide vane is considered towards the axis,whereas that for the acting propeller is considered towards the plane ofrotation.

It has been found that the most important of these three parameters isthe increase in relative curvature of the section. Any considerableincrease. in the other two factors is liable to increase excessivelytheaxial length of the unit which is always undesirable, butparticularly so in the case of a multi-stage unit.

According to the present invention a guide vane of aerofoil or laminarsection and for operation in conjunction with an acting propellerarranged in advance or behind the same has the relative curvature of thevane section increased continuously from the hub to the tip. Aerofoil is"wing-shaped body whose main function is to produce lift."

The width of the guide vane preferably increases continuously from thehub to the tip.

whilst the geometric pitch preferably increases continuously from thehub to the tip.

The improved guide vane'is equally applicable either at the inlet or theoutlet endof the acting propeller.

In both cases the purposes of the improved guide vane is to obtain axialdirection of outflow from the unit, in order to utilise fully theinevitable rotational momentum in the slipstream. Any residualrotational momentum which may remain in the outflow, in whateverdirection, is liable to reduce considerably the overall emciency of theunit.

It has been found that with axial outflow the same sections and the sameangles of inclination to the axis of the vanes are essential. whateverthe position of the guide vane, whether in ad- Vance of the vanes orafter them.

In both cases the concave side of the vane faces the direction ofrotation. I I

The only difference between the inlet and outlet vanes is that theoutlet vanes have positive angles of inclination to the axis, whilst theinlet vanes are placed at negative-angles to the axis. Positive anglesare those formed with the axis and the direction of rotation, theleading edge of the vane being always assumed to lie on the axis.Negative angles are those formed in the opposite direction.

The experiments which have been made with a guide vane designed inaccordance with this invention have been found to justify fully thetheoretical investigation, set out above. In some instances the pressureincrease obtained by the use of the guide vane was even greater thanthat attained with an acting propeller alone.

Referring to the accompanying drawings, which illustrate the inventionby way of example:

Fig. 1 shows a front elevation of a guide vane which is adapted for usein screw fans of the medium pressure type.

Fig. 2 shows a sectional side elevation of Fig. 1.

Fig. 3 shows cross sections to a large scale of a vane Fig. 4 is a graphin which are indicated the percentage values of the vane parametersalong the vane.

Referring now to Fig. 1, the vanes I, of a guide vane are fixed to a,central hub 2, the relative diameter of which corresponds exactly withthat of an acting propeller in order to ensure uninterrupted flow. Theleading edge 3 and the trailing edge 4 are not directed radially inorder to avoid sound interference with the rotating blades of the actingpropeller, thereby reducing noise to a minimum.

The guide vane may be manufactured as a one piece casting or may bewelded from separate parts, or cast blades may be bolted to the centralhub 2 and to the tip shroud 5.

The cross sections 6, I, 8, 9, l0, II correspond respectively with theradial distances 1.0, .9, .8, .7, .6, .55 (Fig. 1) from the centre l5 ofthe propeller.

In Fg. 4 the curve I2, shows the percentage increasv of the relativecurvature of the cross sections of the vanes from the hub to the tip.

The curve I3 shows the increase of the blade width from the hub to thetips.

What I claim as my invention and desire to secure by Letters Patentis 1. A reactin propeller having vanes of aerofoil cross sections to beused in conjunction with an acting propeller or propellers, such asrotors for screw fans, pumps, turbines and the like, wherein therelative curvature of each of the vanes of the reacting propellerincreases continuously from the hub to the tip.

2. A guide vane having vanes of aerofoil crosssections to be used inconjunction with an acting propeller or propellers, such as rotors forscrew fans, pumps, turbines and the like, wherein the relative curvatureof the vanes of the guide vane increases continuously from the hub tothe tip, and the width of the vanes increases continuously from the hubto the tip.

3. A guide vane having vanes of aerofoil crosssection to be used inconjunction with an acting propeller or propellers, such as rotors forscrew fans, pumps, turbines and the like, wherein the relative curvatureof the vanes of the guide vane increases continuously from the hub tothe tip, and the width of the vanes increases continuously from the hubto the tip and wherein the geometric pitch of the vanes increasescontinuously from the hub to the tip.

MICHAEL THADDIUS ADAMTCHIK.

' file of this patent:

UNITED STATES PATENTS Number Name Date 345,761 Bennett July 20, 18861,471,590 Carter Oct. 23, 1923 2,097,390 DeMey Oct. 26, 1937 2,224,519McIntyre Dec. 10, 1940 2,384,000 Wattendorf Sept. 4, 1945 FOREIGNPATENTS Number Country Date 216,170 Great Britain May 29, 1924

